In order to cancel your game subscription to Darkfall: Rise of Agon, please first log into your account here -

Once logged in, go to the drop down menu at the top right and hit "Manage Account".

Once on the Account Summary page, look under Game Subscription and click "Cancel".  This action will cancel recurring subscription, you will still be able to play on the account for the remaining time purchased if there is any. 

If you are using Paypal and would like to manually cancel you can log in through paypal and cancel the subscription there -

If you are having any issues or questions surrounding subscriptions and cancellation please submit a ticket here.